Many people are worried about global warming today. They fear that the polar ice caps will melt, raising sea levels and creating environmental chaos. Such concerns are not new. The historical record tells us of many warming episodes — and subsequent cooling periods — that have bedeviled humans for thousands of years.
The ancient Greek philosopher Plato, who lived from 427 B.C. to 347 B.C., wrote about major climate changes that were known in his day. In the dialogue "Timaeus," he argued that global warming occurs at regular intervals, often leading to great floods. Said Plato: "When ... the gods purge the earth with a deluge of water, the survivors ... are herdsmen and shepherds who dwell on the mountains. But those who ... live in cities are carried by the rivers into the sea."
In the dialogue "Critias," Plato wrote about weather-related geological changes. He referred to "formidable deluges" that washed away all the topsoil, turning the land into a "skeleton of a body wasted by disease." What were now plains had once been covered with rich soil, Plato said, and barren mountains were once covered with trees. The yearly "water from Zeus" had been lost, he went on, creating deserts where the land was once productive.
Plato's student, Aristotle, who lived from 384 B.C. to 322 B.C., also recorded evidence of global warming in his work "Meteorologica." He noted that in the time of the Trojan War, the land of Argos was marshy and unarable, while that of Mycenae was temperate and fertile.
"But now the opposite is the case," Aristotle wrote. "The land of Mycenae has become completely dry and barren, while the Argive land that was formerly barren, owing to the water, has now become fruitful." He observed the same phenomenon elsewhere covering large regions and nations.
Theophrastus, a student of Aristotle who lived from 374 B.C. to 287 B.C., discussed climate change in his work "De ventis," which means "The Wind." He observed that, in Crete, "nowadays the winters are more severe and more snow falls." In earlier times, Theophrastus said, the mountains there bore grain and fruit, and the island was more populous. But when the climate changed, the land became infertile. In his book, "De causis plantarum," Theophrastus noted that the Greek city of Larissa once had plentiful olive trees, but that falling temperatures killed them all.
In the first century A.D., an ancient Roman named Columella wrote an agricultural treatise called, "De re rustica." In it, he discussed global warming that had turned areas once too cold for agriculture into thriving farm communities. Columella cites an authority named Saserna, who recorded many such cases. According to Saserna, "regions which formerly, because of the unremitting severity of winter, could not safeguard any shoot of the vine or the olive planted in them, now that the earlier coldness has abated and weather is becoming more clement, produce olive harvests and the vintages of Bacchus (wine) in greatest abundance."
In the Middle Ages, people began recording the temperature and climate-related phenomena, such as the dates when plants began to blossom annually. They were aware of a warming trend that began around 900 and a cooling trend that began around 1300. We know that during the warm period, the Vikings established settlements in Greenland, where perpetual ice had previously covered the land. Ancient Norse records tell us that these settlements were abandoned after 1250, when falling temperatures made farming less viable and spreading ice in the sea made transportation more difficult.
The cooling trend led to heavy rains in 14th century Europe that were too much for the crops, leading to reduced agricultural output and numerous famines. In the 15th century, a warming trend returned, which lasted until the middle of the 16th century, when temperatures again started to fall.
By the 17th century, it was clearly apparent that a cooling trend was altering sea routes, and changing the kinds of crops farmers could grow, fishing patterns and so on. Glaciers began to advance rapidly in many places, and rivers that had long been ice-free year round started to freeze in the winter. This "little ice age" continued well into the 19th century. Since then, we have been in a warming cycle that appears to have accelerated around 1950.
The point of this review is that we know a great deal about climate changes from the historical record and need not rely solely on scientific studies of core samples, tree rings and so on. These changes occurred long before industrialization and could not possibly have been manmade in any way whatsoever. They don't prove that man is not now affecting the climate through carbon dioxide emissions, but they do tell us that temporary warming trends are common in human history. It may only be a matter of time before another cooling trend comes along.
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